Explosive comprising polynitro heterocyclic and nitroaromatic compounds



United States Patent 3,140,212 EXPLOSIVE COMPRISING POLYNITRO HETERO-CYCLIC AND NITROAROMATIC COMPOUNDS Elbert E. De Maris, Mantua, N.J.,assignor to E. I. du Pont de Nemours and Company, Wilmington, Del., acorporation of Delaware No Drawing. Filed Mar. 28, 1963, Ser. No.268,554 5 Claims. (Cl. 149-106) The present invention relates to highexplosive compositions capable of being compressed readily into denseshaped articles having high thermal stability and compressive strength.

In oil-well perforating operations, it is desirable to use an explosivein the form of dense shaped articles having sufiicient compressivestrength to obviate the need for a supporting container, and highthermal stability, so that the explosive is not adversely affected bythe temperatures encountered in the wells, i.e., temperatures exceeding350 F. High density is desirable since the higher the density, thecloser the explosive properties approach theoretical.

It recently has been discovered that tetranitro derivatives of certaindibenzotetraazapentalenes, i.e., tetranitro-2,3; 5,6-dibenzo-1,3a,4,6a-tetraazapentalene and tetranitro-2,3;4,S-dibenzo-1,3a,6,6a-tetraazapentalene, are explosive compounds ofunusually high thermal stability. The Working of these compounds intoshaped articles presents considerable difficulty, however. In order toproduce dense articles therefrom, i.e., articles having a density of atleast about 1.70 grams per cubic centimeter, it is necessary to applyextremely high compressive pressures, e.g.,about 40,000 pounds persquare inch, to the material over extended periods of time, e.g., forabout O.52 hours.

The present invention provides new explosive compositions which can becompressed readily into dense shaped articles of strength, stability,and explosive properties equivalent to those of articles made fromcompositions consisting solely of the aforementioned tetranitrocompounds.

Thecompositions of this invention comprise a mixture of at least onepolynitro heterocyclic compound selected from the group consisting oftetranitro-2,3;5,6-dibenzo-1,

3a,4,6a-tetraazapentalene andtetranitro-2,3;4,5-dibenzol,3a,6,6a-tetraazapentalene and from about 1to 20%, based on the weight of the mixture, of at least one aromaticcompound of 6. to 7 carbon atoms bearing 3 nitro groups as the soleinorganic substituents, that is, a trinitrobenzene, a trinitrotoluene,or a mixture thereof.

Of the aromatic trinitro additives, trinitrobenzenes are preferredbecause of their thermal stability. Of the isomeric trinitrobenzenes,1,3,5 -trinitrobenzene is particularly preferred because of the optimumprocessing qualities it imparts to compositions of this invention,because of the optimum strength and stability of products formedtherewith and because of its ready availability.

The explosive compositions of this invention can be formed into shapedarticles having a density of at least about 1.70 grams per cubiccentimeter by application ofcompressive pressures of only 10,000 poundsper square inch for a period of only 10 minutes. When higher pressuresare used, the application time need be only 1 minute. In contrast tothis, the aforementioned polynitro heterocyclic compounds per se requiremuch severer conditions applied over longer periods to reach suchdensities. In addition, at pressures of 40,000 pounds per square inchthey reach a maximum density after two hours application time which islower than the density attained in 1 minute with the novel compositionsof this invention. In addition to having high density, shaped articlesproduced from the present com- 3,140,212 Patented July 7, 1964 u e N 6Nand Obviously there are numerous possible isomers of these compoundsbased upon the relative positions of the nitro groups on each benzenering. All of the possible isomers of each compound are believed to bepresent to a greater or lesser extent in each product. For purposes ofthe present invention, there is no material distinction between any suchisomers, i.e., the stability and explosive properties of these isomersappear to be quite similar .and the novel compositions of this inventionmay include any of these isomers individually or a combination of anysuch isomers in any proportion. Actually, separation of the isomers isvery difiicult because of the similarity in their properties andsynthesis of either of the compounds Would normally result in a mixtureof isomers. This is satisfactory insofar as explosive applications areconcerned and the product may be used directly in this form. Throughoutthis application, reference to the two tetranitro compounds isunderstood to include any and all such isomers and/or any mixture ofsuch isomers in any proportion.

The tetranitro-2,3 ;5,6-dibenzol ,3a,4,6a-tetraazapentalene can beprepared by mixing one part of 2,3;5,6-

dibenzo-l,3a,4,'6a-tetraazapentalene in concentrated sulfuric acid with30 parts of red fuming nitric acid with slight cooling, allowing it toreact for 15 minutes at about ambient temperature, heating the resultingproduct at 60 C. for an additional 15 minutes, then precipitating thetetranitro derivative by cooling the reaction mixture and pouring itinto five times its volume of ice water. The2,3;5,'6-dibenzo-1,3a,4,6a-tetraazapentalene can be prepared asdescribed in Reissue Patent No. 25,238. Thetetranitro-2,3;4,5-dibenzo-1,3a,6,6a-tetraazapentalene can be preparedby similar procedures from 2,3;4,5-dibenzo-l,3a,6,6a-tetraazapentalene.As described more fully in copending application Serial No. 252,059,filed January 17, 1963, 2,3;4,5-dibenzo-1,3a,6, 6a-tetraazapentalene canbe prepared by reducing l-(o-nitrophenyl)-1,2,3-benzotriazole tol-(o-aminophenyl)-l,2,3- benzotriazole, reacting the resulting productsuccessively with an alkali metal nitrite and an alkali metal azide inthe presence of a strong acid to yield the corresponding azidoderivative and heating such azido derivative at a temperature of atleast about 100 C.

The ingredients of the present explosive composition can be mixedtogether inany convenient manner. For example, the polynitroheterocyclic compound can be mixed with a solution of trinitrobenzene ortrinitrotoluene in a polar'solvent, e.g., a ketone, ester, or alcohol,and the solvent thereafter evaporated. Alternatively, the polynitro'heterocyclic compound can be mixed with molten trinitrobenzene ortrinitrotoluene, and the latter then allowed to solidify.

The compositions of this invention can contain the aforementionedpolynitro heterocyclic compounds and aromatic nitro additive alone or incombination with other conventional additives, for example, inorganicoxidizing agents such as potassium perchlorate and lead dinitrate,preferably inamounts up to 10% by weight. Larger amounts of suchadditives also may be employed, however, for examplea stoichiometricamount of oxidizing agent, e.g., about 65% potassium perchlorate. Also,up to 10% by Weight of auxiliary binding agents such as those describedin copending application Serial No. 118,260, filed June 20, 1961, nowUS. Patent No. 3,089,796, can be added thereto.

As stated previously, the amount of trinitrobenzene or trinitrotoluenein the present explosive compositions can vary from about 1% to about20% by weight. Generally, optimum thermal stability and ease ofcompressing into dense shaped objects are found in compositionscontaining from about 2% to about 5% of the aromatic trinitro compound,and such compositions are preferred. In addition to these, desirablecompositions are those containing as little as 1% of trinitrobenzene ortrinitrotoluene and small quantities of other additives, such as thosementioned above, which may enhance the compressibility of thecomposition. Compositions containing less than 1% of the aromatictrinitro compound are not desirable because the forming of shapedarticles therefrom begins to require severe conditions of pressure andtime. The aromatic trinitro compound can be used in amounts up to about20% .by weight of the composition, if a lowered thermal stability can betolerated. Compositions containing greater than 20% of trinitrobenzeneor trinitro toluene do not exhibit the outstanding thermal stability ofthe compositions of this invention. In compositions containingsubstantially more than about 5% of the are- 'matic trinitrocompound, itmay be helpful to incorporate small amounts of a gelling agent such assilicon dioxide to prevent leakage of the trinitro compound from thecomposition during pressure at elevated temperatures.

The preparation of shaped articles from the present explosivecompositions can be effected in any desired manner. No binder materialis required. As is shown in the following examples, the compositions canbe formed into shaped articles of density greater than 1.70 grams 'percubic centimeter when pressures of 10,000 pounds per square inch areapplied for minutes. Higher pressures require less compression time.Generally, it is helpful to heat the mixture at about 150 to about 225C. during compression, and also to preheat at this temperature for aminute or so prior to compression.

By employing a suitably shaped mold, shaped articles of any desiredconfiguration can be obtained. Thus, the compositions of this inventioncan be shaped into briquette-like pellets useful as such as a highexplosive or as a mold charge to make other shaped articles. By using acylindrical mold with a conical protrusion in one end thereof, shapedcharges can be prepared. Such shaped charges can be either used per seor with a metallic liner 'in the conical indentation therein asdescribed, for

example, in US. Patents 2,399,211 and 2,563,131. The compositions ofthis invention can also be compressed into polyhedral or cylindricalblocks which can be used as high temperature explosive charges or asprimers.

To more fully describe the preparation and properties of the newexplosive compositions of this invention, reference is now made to thefollowing examples which are intended to be illustrative only and not aslimiting the invention in any manner.

In the examples, a Dillon Model L Universal Testing Machine with acompression cage, 010,000-pound dynamometer, and powered with an airmotor was used to compress the pellets. The compressive strength wasdetermined according to ASTM Test Method D6 95-54, as described in ASTMStandards, 1958 Edition, Part 9, pages 244-251.

Example 1 (A) A solution of 1 gram of 1,3,5-trinitrobenzene in 5milliliters of acetone is poured over 19 grams of tetranitro 2,3;5,6dibenzo-1,3a,4,'6a-tetraazapentalene which has been wetted with 10milliliters of acetone. After stirring for 2-3 minutes to insure auniform mixture, the acetone then is evaporated on a steam bath whilethe mixture is stirred leaving 20 grams of an orange-red powder. Todetermine the thermal behavior of the composition, a 25-60 milligramsample is heated at a rate of 7.5 C. per minute. The trinitrobenzeneportion melts at 123 (3., there is evidence of some decompositionbeginning at 325 C., and the major part of the sample decomposes at 379C.

Two and one-half gram portions of the powder are pelleted in a die at200 C. The die is tapered, having a maximum diameter of 0.5 inch and amaximum depth of 0.5 inch. The powder is heated in the die for 1 minuteat 200 C., and then is pressed at the same temperature by application of10,000 pounds per square inch pressure for a period of ten minutes. Thepellets are then ejected from the die while hot. They have a density of1.754

grams per cubic centimeter, and exhibit compressive strengths of about4400 pounds per square inch. The pelleted composition can be initiatedby a conventional blasting cap, and detonates at a velocity of 6,930meters per second.

To test explosive power, a pellet is placed on a 0.5-inch thick 1018cold-rolled steel plate, which in turn rests on a larger plate made ofthe same material. The pellet is initiated by a conventional blastingcap, and theresulting dent made in the steel is measured to the nearestthousandth inch. The dent value for this pellet is 0.059 inch, the sameas the value obtained with a pellet oftetranitro-2,3;5,6-dibenzo-1,3a,4,'6a-tetraazapentalene of density 1.67grams per cubic centimeter.

(B) To contrast these results with the results obtained whentetranitro-2,3;5,6-dibenzo-1,3a,4,=6a-tetraazapentalene alone is formedinto pellets, thetetranitro compound is pelleted in the same way as thecomposition described in A. The density is only 1.28 grams per cubiccentimeter, and the compressive strength 1000 pounds per square inch.The detonation velocity is 4500 meters per second.

Example 2 The procedure of Example 1(A) is repeated while varying one ormore of the conditions, e.g., pressure, compression time, andcomposition pelleted. The results are shown in the following table.

Example 3 Pellets having a density, compressive strength, thermalproperties, detonation velocity, and explosive power comparable to thoseof the pellets described in Example 1(A) are obtained when the procedureof Example 1(A) is repeated with the exception that tetranitro-2,3;4,5-dibenzo- 1,3a,6;6a-tetraazapentalene is substituted for thetetranitr0-2,3;5,*6-dibenzo-1,3a,4,6a-tetraazapentalene. Similarly, theprocedure of Example 1(A) can be repeated except that an equal weight ofTNT is substituted for the trinitrobenzene used in that example.

I claim:

1. An explosive composition comprising a mixture of at least onepolynitro heterocyclic compound selected from the group consisting oftetranitro-2,3;5,6-dibenzo-1, 3a,4;6a-tetraazapentalene andtetranitro-2,3;4,5-dibenzo- 1,3a,6,6a-tetraazapentalene and about from 1to 20%,

based on the weight of said mixture, of at least one aromatic compoundof 6 to 7 carbon atoms bearing 3 nitro groups as the sole inorganicsubstituents.

2. A composition of claim 1 wherein said aromatic compound is1,3,5-trinitrobenzene and is present in the amount of about 2 to 5%.

3. A composition of claim 2 wherein said polynitro heterocyclic compoundis tetranitro-2,3;5,6-dibenzo-1,3a, 4,'6a-tetraazapentalene.

4. A composition of claim 2 wherein said polynitro heterocyclic compoundis tetranitro-2,3;4,S-dibenzo-l,3a, 6,6a-tetraazapentalene.

5. A shaped article having a density of at least about 1.70 grams percubic centimeter comprising a compressed composition of claim 1.

No references cited.

1. AN EXPLOSIVE COMPOSITION COMPRISING A MIXTURE OF AT LEAST ONE POLYNITRO HETEROCYCLIC COMPOUND SELECTED FROM THE GROUP CONSISTING OF TETRANITRO-2,3;5,6-DIBENZO-1, 3A,4,6A-TETRAAZAPENTALENE AND TETRANITRO-2,3,-4,5-DIBENZO1,3A,6,6A-TETRAAZAPENTALENE AND ABOUT FROM 1 TO 20%, BASED ON THE WEIGHT OF SAID MIXTURE, OF AT LEAST ONE AROMATIC COMPOUND OF 6 TO 7 CARBON ATOMS BEARING 3 NITRO GROUPS AS THE SOLE INORGANIC SUBSTITUENTS. 